The present invention relates generally to measuring fluid flows. More particularly the invention relates to a device according to the preamble of claim 1 and a method according to the preamble of claim 11. The invention also relates to a computer program according to claim 19 and a computer readable medium according to claim 20.
Measuring a liquid flow is a relatively straightforward task provided that the flowing medium is homogenous, i.e. if there is only a single substance present in the conduit where the flow is to be measured. However, in practice, it is often the case that the flowing medium is non-homogenous, i.e. there is more than one substance present in the conduit. Moreover, the proportions between the different constituents in the flow may vary over time. As a result, it can be rather complicated to determine relevant flow measures. To mention a few examples, such liquid flows are common in milk extraction and transport, and in the oil and gas industry.
The prior art contains various examples of flow measurement solutions. For example WO 01/29518 discloses a solution for carrying out measurements of a pulsating milk flow in a line. Thus, here, the measured medium comprises a gas and a liquid. The line has a measuring region in which at least one parameter of the medium is determined during a measurement. The measuring region, in turn, may contain a measuring chamber in which milk remains after a pulse flow. This allows further analysis of the milk, such as color analysis.
U.S. Pat. No. 5,116,119 reveals a solution for measuring milk flows, wherein the liquid is directed to flow through one or more flow channels, while exposing the liquid to electromagnetic radiation. The liquid's transparency to electromagnetic radiation is used to determine a momentary volume of the liquid flowing through each flow channel. The momentary velocity of the liquid flowing through the flow channels is also determined, thereby permitting a determination of the momentary flow rate of the liquid flowing through the flow channels.
EP 1 155 610 describes a quantity meter for determining the quantity of liquid flowing through a line. The quantity meter has two electrically conductive elements arranged in the line at a fixed measuring distance from each other. The conductive elements are connected to an electronic circuit. The diameter of the line is such that when the liquid is flowing there through the volume of the line across the measuring distance is completely filled for some time. Furthermore, in the electronic circuit the quantity of liquid flowing through is determined based on the measured electric conductivity of the liquid therein.
U.S. Pat. No. 7,155,971 shows a device for determining the volumetric flow rate of milk flowing during a milking process. Here, a cross-sectional area of the milk flow is determined at a first measuring point by means of a sensor, which is arranged outside the flowing milk. The time required by the milk flow, with the determined cross-sectional area, to go from the first measuring point to a second measuring point provided downstream from the first measuring point is measured. The flow speed is then derived from the measured time and the known distance between the first and second measuring points. The volumetric flow rate is determined on the basis of the determined cross-sectional area and the flow speed.